The present invention relates to a voltage controlled oscillator and more particularly to such an oscillator which is operable over a wide and accurately definable range of frequencies.
In various analog control systems, it is often desirable to utilize a voltage controlled oscillator. For example, in resonant mode power supplies, an electronic switch is periodically turned on applying a pulse of current to a resonant tank circuit. The input power to the tank circuit is controlled by varying the rate of pulsing, e.g. by means of a voltage controlled oscillator, in response to a control voltage. The control voltage is typically the output of an error amplifier which compares the power supply output voltage to a known reference. It is desirable that the voltage controlled oscillator in such an application have a wide dynamic range and the ability to operate at a relatively high frequency, e.g. greater than one megahertz. Further, the operating characteristics of the voltage controlled oscillator should be stable with temperature and it is desirable that the maximum and minimum frequencies can be accurately selected or defined.
Among the several objects of the present invention may be noted the provision of a voltage controlled oscillator which is operable over a wide dynamic range; the provision of such an oscillator whose operating characteristics are stable with temperature; the provision of such an oscillator which is operable at high frequency; the provision of such an oscillator which has a highly linear response; the provision of such an oscillator whose minimum and maximum frequencies can be externally defined by relatively simple means; the provision of such an oscillator which is highly reliable and which is of relatively simple and inexpensive construction. Other objects and features will be in part apparent and in part pointed out hereinafter.